The invention relates to a microdialysis probe. Dialysis probes of this kind are described in SE-C-434 214, U.S. Pat. No. 5,735,832 and U.S. Pat. No. 5,741,284.
The meaning of specific wordings in this text should be interpreted as follows: The word probe should be interpreted also as catheter. The inlet and outlet of the probe as described may in case of a reversed flow be used as outlet and inlet, respectively.
Perfusion liquid is the liquid used in the microdialysis, which is allowed to enter the probe and there take up substances from the surrounding tissue through a membrane. The perfusion liquid becomes the dialysate after the dialysis. Deformable mesh is to be interpreted as further described in the application below.
Microdialysis is a method of examination in which a probe is inserted into tissue in vivo, such that one side of a semi-permeable membrane is in contact with tissue and extra cellular liquid and the other side is flushed or rinsed with a dialysis liquid (perfusate) which takes-up substances from the extra cellular liquid through the membrane. These substances can then be analyzed in the dialysate on or after exiting the probe.
Microdialysis probes are by nature fragile, which requires great care in inserting and withdrawing the probe from the tissue in which it is used. At least part of the probe needs to have a surface consisting of a thin permeable membrane, which may be broken particularly when removing the probe. For insertion of the probe there exists insertion means such as an external tube or the like that may be used to protect the probe during insertion. The insertion means, if such means are used, are removed before the actual use of the probe if such are used.
However, when inserted into tissue of a living person, the probe must be able to retain its shape despite the stresses and strains to be expected when/if the person moves (even if the person is quite still there may still be movements in e.g. a muscle) and at withdrawal of the probe.
The use of microdialysis becoming more frequent and common raises other problems such as monitoring and control of the probe during insertion and use. It is a fact that microdialysis provides a unique possibility to examine the equilibrias of substances and/or the amounts present or missing of substances or to monitor specific changes in the status of substances connected with e.g. the use of medicaments, in surgery etc.
The monitoring and control of the probe position during insertion/withdrawal and use has been an obstacle in so far that the smallness and the material of the probe does not make possible the use of common methods for detecting the probe once the insertion has been started. This becomes more problematic the deeper into the tissue the microdialysis is to take place.
It is thus an object of the invention to provide a microdialysis probe, which is suitable for the general use in living tissue when taking samples for e.g. diagnostic purposes. In particular the object is an improved probe, which may withstand forces acting on the probe during use and withdrawal of the same.
A further object is to give good access to the membrane for the intracellular liquid and still be able to protect the membrane and to be able to retract the probe in full.
A further object of the invention is to provide a microdialysis probe, the location of which may be monitored and controlled using means such as X-rays or the like during insertion/withdrawal or during dialysis in order to facilitate the placement of the probe at a predetermined location and to control the location of the probe.
In accordance with the invention, these and other objects evident from the description of the invention are accomplished in a microdialysis probe in that a deformable mesh sleeve is adapted to enclose and protect at least said dialysis membrane, the proximal end of said deformable sleeve fastened to the probe between the proximal end of the probe and the dialysis membrane, and in that said deformable mesh sleeve when subjected to a pulling action in the longitudinal direction of the sleeve is deformed such that the diameter of said sleeve decreases.
The wording enclose should be understood such that the mesh sleeve always is secured to the proximal part of the probe but the other end of the sleeve may be either open-ended or closed or attached to the distal part of the probe as such.